Update secp256k1 requirement from 0.28 to 0.29

---
updated-dependencies:
- dependency-name: secp256k1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -29,7 +29,7 @@ serde_json = "1.0.39"
 tiny-keccak = { version = "2.0.1", features = ["keccak"] }
 pin-project = "1.0"
 # Optional deps
-secp256k1 = { version = "0.28", features = ["recovery"], optional = true }
+secp256k1 = { version = "0.29", features = ["recovery"], optional = true }
 once_cell = { version = "1.8.0", optional = true }
 
 ## HTTP